1. Field of the Invention
This invention relates generally to nonfragmenting rupture disk assemblies and methods, and more particularly, to improved such assemblies and methods wherein the rupture disk ruptures into a hinged blow-out portion which is caught and prevented from moving and tearing by pressure relieving fluid flow.
2. DESCRIPTION OF THE PRIOR ART
A variety of safety pressure relieving assemblies of the rupture disk type have been developed and used heretofore. Generally, the assemblies include a rupture disk supported between inlet and outlet supporting members, the inlet supporting member being connected to a relief connection of a vessel or system containing fluid pressure. When the fluid pressure within the vessel or system exceeds the design rupture pressure of the disk, the disk ruptures causing fluid pressure to be relieved from the vessel or system through the ruptured disk and the outlet supporting member.
Various types of rupture disks have heretofore been used including rupture disks which are formed of single parts and composite rupture disks formed of several parts. For example, single part rupture disks which are flat or which include domed portions have commonly been used heretofore. Composites of such rupture disks and other complimentary components such as vacuum supports and disk cutting members have also commonly been used.
Domed rupture disks generally include a central concave-convex portion. Domed rupture disks in which the concave sides of the disks are exposed to fluid pressure are commonly known as "conventional" rupture disks. Conventional rupture disks are placed in tension by the force of the fluids under pressure exerted thereon, and rupture occurs when the tensile strength of the disk material is exceeded. Domed rupture disks in which the convex sides of the disks are exposed to fluid pressure are known as "reverse buckling" disks. Reverse buckling rupture disks are placed in compression by the fluid pressure exerted thereon, and typically, when the design rupture pressure of the disk is exceeded, the concave-convex portion first reverses itself and then ruptures.
Cutting members including cutting edges of various configurations have been utilized with composite reverse buckling rupture disks to puncture the disks upon reversal and bring about the full opening thereof. For example, U.S. Pat. No. 4,236,648, assigned to the assignee of this present invention, which is incorporated herein by reference for purposes of disclosure, is directed to a composite rupture disk comprised of a reverse buckling rupture disk attached to a cutting member which includes a partially circular cutting edge. Upon reversal of the reverse buckling rupture disk, the cutting edge is contacted by the disk which severs the disk and forms a hinged blow-out portion therein.
One or more lines of weakness formed by scores or grooves which define one or more blow-out portions have been utilized in both conventional and reverse buckling rupture disks. The blow-out portions can take a variety of configurations and can be hinged to the remainder of the disks by areas not including lines of weakness. Upon rupture, the disks tear along the lines of weakness whereby the fragmentation of the disks is substantially prevented.
While the heretofore utilized rupture disk assemblies have been successfully used in a great number of applications, problems are still encountered. A particular such problem involves the fragmentation of the blow-out portions of the disks due to the pressure relieving fluid flow through the ruptured disks and the outlet supporting members which imparts a whipping action to the blow-out portions. The whipping action in turn causes pieces of the blow-out portions to fragment or sever which can damage or contaminate downstream processes and/or equipment into which the fragments are carried.
A number of solutions to this fragmentation problem have been proposed and utilized substantially successfully. For example, U.S. Pat. No. 5,167,337, which is assigned to the assignee of the present invention and which is incorporated herein by reference for purposes of disclosure, is directed to a rupture disk assembly including a reverse buckling rupture disk having a line of weakness formed by a C-score therein which defines a hinged blow-out portion. A rupture disk hinge supporting surface is provided which extends into the concave portion of the rupture disk and functions to slow the rupture process and to support the hinge area whereby tearing and fragmentation of the blow-out portion does not occur.
U.S. Pat. No. 5,005,722, also assigned to the assignee of this present invention and incorporated herein by reference for purposes of disclosure, is directed to a reverse buckling C-scored rupture disk assembly which includes a notch removed from a portion of the inlet supporting member to cause disk failure at reduced pressures when the assembly is inadvertently installed upside down. In addition, the assembly includes a hinge supporting member to prevent fragmentation of the C-shaped blow-out portion produced when the rupture disk ruptures during normal operation.
While the above described rupture disk assemblies and other prior art assemblies have been utilized successfully to reduce the incidence of fragmentation, some fragmentation still occurs as a result of the blow-out portions of the rupture disks still being subjected to the above mentioned whipping action. The incidence of such fragmentation increases as the size of the rupture disk increases and the design rupture pressure thereof decreases. That is, a large diameter, low pressure rupture disk is more likely to produce such fragmentation upon rupture than is a smaller higher pressure disk. This is because upon rupture, the blow-out portion of a large diameter, low pressure rupture disk which is formed of thin material, is readily moved and whipped about by the pressure relieving fluid flow through the ruptured disk and the outlet supporting member.
Thus, there is a need for improved nonfragmenting rupture disk assemblies and methods which prevent the above mentioned whipping action and the fragmentation incident thereto.